When managing I/O requests from clients to data stored in units of blocks on storage devices based on a metadata tree structure including a root node directly or indirectly pointing to blocks e.g. via indirect nodes pointing to direct nodes and via direct nodes pointing to blocks of data, in particular in connection with a log write method which writes modified data to newly allocated blocks, it has been recognized that by referring to the metadata nodes by processing the metadata tree structure may lead to significant read and write amplifications due to random reads and/or random writes in connection with metadata nodes.
In view of the above problem, it is an object of the present invention to provide aspects in a data storage system, which provides and updates a metadata tree structure of plural metadata nodes for managing I/O requests, allowing to reduce or avoid read and write amplifications, preferably while achieving high efficiency in handling I/O requests from a high number of clients and in connection with multiple types of I/O access protocols, economical use of storage resources and memories, efficient scalability for clustered systems of multiple node apparatuses, highly reliable and efficient data consistency and data protection, and efficient and reliable recovery functions in case of failures.